Question Bank • QB_EXP_IDE_ETP_002
MCQ • 1 Mark
Section 5: Irrigation and Drainage Engineering
Evapotranspiration, Consumptive Use & Crop Water Needs
Subtopic: FAO Penman-Monteith method reference surface
Question Statement:
The FAO-56 Penman-Monteith standard reference surface is defined as a hypothetical green grass reference crop having an assumed height of:
Options:
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(A) $0.12\text{ m}$ with fixed surface resistance of $70\text{ s/m}$ and albedo of $0.23$
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(B) $0.50\text{ m}$ with surface resistance of $100\text{ s/m}$ and albedo of $0.15$
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(C) $0.05\text{ m}$ with surface resistance of $30\text{ s/m}$ and albedo of $0.05$
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(D) $1.00\text{ m}$ with surface resistance of $50\text{ s/m}$ and albedo of $0.35$
Step-by-Step Solution & Explanation
FAO-56 standard reference crop is an extensive surface of green, well-watered grass of uniform height of $0.12\text{ m}$, aerodynamic resistance $r_a = 208/u_2\text{ s/m}$, fixed canopy resistance $r_s = 70\text{ s/m}$, and reflection coefficient (albedo) $\alpha = 0.23$.
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